(1) Field of the Invention
The present invention relates to a gateway apparatus to be connected to a plurality of user terminals, more particularly, to a gateway apparatus with an LAC (L2TP Access Concentrator) function to be applied to an ISP (Internet Service Provider) selection type IP network connecting a plurality of ISP networks connected to the Internet by an access network, in which a user terminal accesses the Internet via the access network and any of the ISP networks.
(2) Description of the Related Art
In nowadays where 70% or more of Internet traffic is occupied by Web access traffic, aiming at increasing the speed of Web access from user terminals and reducing traffic on a network connecting user terminals and Web servers, Web caching is being actively studied.
In the Web caching technology, a Web cache server (or Web caching server) is connected to an access network accommodating user terminals, a part of contents data provided by a Web server is stored as cache data in the Web cache server, and the contents data is distributed from the Web cache server in place of the Web server to the user terminals, thereby realizing increase in speed of an access to the Web from a user terminal and reduction in traffic on a core network to which the Web server is connected.
Conventionally, in the field of a network for accessing the Internet, each ISP has its own access points distributed in its service areas. Recently, an. ISP selection type IP network is becoming promising, in which a plurality of ISP networks are connected to a regional IP network (or wide area IP network) managed by a communication carrier, gateway apparatuses as access points commonly used by the plurality of ISPs are disposed on the regional IP network, and user terminals connected to each of the access points are selectively connected to any one of the ISP networks.
In the ISP selection type IP network, a gateway apparatus called an LAC (L2TP Access Concentrator) is installed at a connection point between the regional IP network as an access network and user terminals, and a gateway apparatus called an LNS (L2TP Network Server) is installed at a connection point between the regional IP network and each of ISP networks.
A user terminal accessing the Web establishes a PPP connection between the user terminal and the LAC. The PPP connection is extended to an ISP network designated by the user through an L2TP connection established between the LAC and the LNS.
Specifically, at the time of establishing the PPP connection, when user ID and the identifier of a terminating ISP are input from the user terminal, the LAC connected to the user terminal specifies an LNS corresponding to the terminating ISP on the basis of the ISP identifier, and extends the PPP connection established between the user terminal and the LAC to the specified LNS through the L2TP connection established between the LAC and the LNS. The LNS authenticates the user ID of the terminal user and determines whether the user terminal and the ISP can be connected to each other or not.
The extension of the PPP connection according to the L2TP and the functions of the LAC and LNS are described in the IETF draft RFC2661.